A fire-fighter carries a self-contained breathing apparatus wherein air is directed from a pressurized supply tank to a face mask through a pressure regulator and a demand inhalation valve connected to the face mask by a flexible breathing tube. A check valve and quick release coupler unit is connected to the pressure regulator and is adapted to be temporarily connected by an adaptor to the flexible breathing tube extending from the face mask of a breathing apparatus on a second fire-fighter to provide for quickly supplying emergency air to the second fire-fighter. Preferably, the adaptor is normally retained and carried in an inactive position by the coupler unit so that it is always available for immediate use.